The invention mainly relates to an elastic-bodied crawler used for construction machines, such as crawler dump truck, hydraulic excavator and the like, and farm machines.
Conventionally, an endless elastic-bodied crawler formed by covering a plurality of metal core members with an organic elastic material (for example, rubber) has been frequently used in crawler vehicles such as construction machines and farm machines. In recent years, however, an elastic-bodied crawler without metal core members has been adopted in terms of recycling after use. FIG. 9(a) is a top plan view showing a concrete example of a conventional elastic-bodied crawler without metal core members and FIG. 9(b) is a cross sectional view taken along the line a—a. The conventional elastic-bodied crawler 100 without metal core members is formed integral as shown in FIGS. 9(a) and 9(b) to comprise driven projections 105, which are provided circumferentially at a predetermined pitch along a center line on an upper surface, and lug portions 102 having a lug 103 formed on an outer surface side (outer peripheral ground surface side) of an endless body 101 having a predetermined width and a predetermined thickness. The body 101 is structurally reinforced by arranging a multiplicity of reinforcement cables 106 near an inner surface of the body over an entire width of the body except ear portions 104 on both sides of the body and over an entire circumference of the body.
The elastic-bodied crawler 100 thus structured is wound around a sprocket and an idler in a traveling section of a crawler vehicle (not shown) to be able to transmit power in a state, in which the driven projections 105 provided on an inner surface of the elastic-bodied crawler 100 at a predetermined pitch engage with engaging teeth provided on a circumferential surface of the sprocket, and a multiplicity of rollers provided between the sprocket and the idler hold a ground surface side of the elastic-bodied crawler 100 from above to be able to ensure a ground force. In addition, the elastic-bodied crawler 100 is so structured that outer peripheral surfaces of the sprocket and the idler bear flat surfaces 107, 107 on both sides of the driven projections 105.
Also, with the elastic-bodied crawler 100, reaction forces during traveling are born by the plurality of rollers 110 provided for the purpose of ensuring a ground force during traveling and the flat surfaces 107, 107 on the both sides of the driven projections 105 provided along a center line on an inner surface of the body, as shown in FIG. 10. In addition, the rollers 110 are mounted on both side portions of a support shaft 112, an intermediate portion of which is rotatably born by a bearing 115 provided and supported on a traveling body frame (not shown), and provided in a manner to contact on both sides thereof with the flat surfaces 107, 107 and to bridge areas where the driven projections 105 are provided.
As described above, with the elastic-bodied crawler 100 wound around the traveling body, load from the rollers 110 is transmitted to a road surface immediately therebelow as it is. At this time, a ground pressure distribution is localized corresponding to projected surfaces of contact portions of the rollers 110, 110, as shown in FIG. 10. As a result, the lug portions 102 on the elastic-bodied crawler 100 undergo local wear, as shown in FIG. 10. When such local wear is generated, there is caused a problem that not only outward appearance is markedly damaged but also the elastic-bodied crawler is consequently shortened in service life because durability of the elastic-bodied crawler 100 is determined by those portions thereof, which are worn violently.
Also, the above elastic-bodied crawler is structured without metal core members such that the driven projections adapted to engage with the sprocket are formed simply from an elastic material (for example, rubber) that constitutes the elastic-bodied crawler. Accordingly, there can be caused an accident that the driven projections come off under the influence of local load due to engagement thereof with engaging teeth on the sprocket in a frequent running drive. When the driven projections come off, there is caused a problem that smooth driving becomes naturally difficult and coming-off portion or portions cannot be repaired for the structural reason of the elastic-bodied crawler, so that it is necessary in this situation to replace the entire elastic-bodied crawler even if a damage portion or portions are limited. Further, there is caused a problem that when the driven projections engage with the sprocket, frictional resistance is increased at locations where contact pressure with a constituent member (elastic material such as rubber) becomes elevated, which is responsible for deterioration and unfavorable generation of sound of abrasion.
The invention has been thought of in order to solve such problems, and has its object to provide an elastic-bodied crawler, in which damages, such as local wear, coming-off of driven projections and the like in use, are prevented from being brought about, and frictional resistance is decreased at engaging portions to provide for durability.